For additional photos and information please check the 'related pages list' at the bottom of this page.
9 June 1937: K XXIII is ordered, but the order might still be cancelled.
21 June 1937: The order for K XXIII is now definite.
12 Oct 1937: K XXIII is laid down at the R.D.M. shipyard in Rotterdam.
At some stage (exact day/year unknown) during the construction the K XXIII is renamed O 23.
5 Dec 1939: O 23 is launched.
10 May 1940: Germany attacks the Netherlands.
O 23 and O 24 are transferred to the Lekhaven docks and camouflaged. In order to keep them out of the hands of German paratroopers.
Naval HQ in 's-Gravenhage reports to the boats that the can not escape to England because the Germans have mined the Waterweg with magnetic mines.
13 May 1940: O 23 is commissioned to the Royal Netherlands Navy, still uncompleted, never submerged and only been tested in few trial(s).
13 May (12 is incorrect) - 1 June 1940: O 23 is under the command of Ltz. I G. Koudijs.
12 or 13 May - 15 May 1940: O 23 sails, still uncompleted and not having been tested in any trials, from Rotterdam to Portsmouth (England) in order to escape from the invading German forces. O 23 is unarmed and there are no torpedoes or deck gun ammo on board
1 June - 28 Sep 1940: O 23 is under the command of Ltz. I G.B.M. van Erkel.
20 May - Sep 1940 or Jun - Jul 1940: O 23 is completed at the John Thornycroft shipyard in Southampton.
5 July 1940: The work on O 23 at the John Thornycroft shipyard is finished (among other things, a loop-aerial is installed) and the submarine leaves for Portsmouth (England). In Portsmouth the boat is demagnetized and four torpedoes are taken on board. O 23 is send to the saver water on the Scottish west coast for her final trials and work-up.
9 July 1940 at 17:00 hrs: O 10 and O 9 depart Portland (England). They are accompanied by the submarines O 23 and the Dutch vessel Z 6 and sail together to Rothesay (Scotland)
11 July 1940: O 9, O 10, O 23 and Z 6 arrive in Milford Haven (England).
12 July 1940: O 9, O 10, O 23 and Z 6 depart from Milford Haven (England).
14 July 1940: O 9, O 10, O 23 and Z 6 arrive in Rothesay (Scotland).
14 July - 26 July 1940: This period is used to for training and work-up of the O 23 crew.
28 July 1940: Escorted by the Dutch vessel Z 6 the O 23 sails via Stornoway to Dundee (Scotland). In Scapa Flow the ship are joined by the RN submarine L 26.
29 July 1940: O 23 arrives in Dundee.
During the transit from John Thornycroft shipyard in Southampton to Dundee the diesel engines of O 23 are producing a lot of oil-smoke. Therefore the 'schraapveren' of both diesels are replaced. In Dundee the starboard 'trustas' is also repaired.
31 July 1940: Because the harbour of Dundee (Scotland) is closed (magnetic mines in the harbour entrance) the O 23 sails to Rosyth (Scotland).
1 Aug 1940: O 23 departs Rosyth and sails to Dundee (Scotland).
15 Aug 1940: O 23 conducts diesel engine trials (see 29 July 1940) North of Bell Rock. After these successful trials the O 23 is ready for her first patrol.
18 Aug - 30 Aug 1940: O 23 patrols the North Sea. No attacks are made.
18 Aug 1940 at 20:30 hrs: O 23 leaves Dundee and heads to an area North of Doggersbank for her work-up patrol.
As expected no ships are spotted. O 23 did hear and see many distant explosions. Later the crew learned that these explosions were from drifting German mines that were part of the Cabbage patch minefield.
30 Aug at 18:15 hrs: The O 23 arrives in Dundee (Scotland).
31 Aug 1940: The complete crew of O 23 is on leave.
1 Sep 1940: The crew of O 23 is called back from their leave because of an expected German invasion. This invasion alarm lasts for three days (until the 3rd of Sept).
3 Sep 1940: The crew of O 23 continues their leave. In the mean time the O 23 is docked in the Camperdown Dock.
7 Sep 1940: The crew of O 23 is called back from their leave once again because of an expected German invasion. The crew prepares the O 23 for a war patrol.
Sep 1940 - Mar 1941: O 23 is attached to the 9th Flotilla in Dundee and is under British operational control.
8 Sep - 22 Sep 1940: O 23 patrols the Skagerrak. No attacks are made.
8 Sep at 06:00 hrs: O 23 departs from Dundee and heads to her patrol area near the entrance of the Skagerrak
Because of this sudden departure date not all personnel was able to return to Dundee in time. Therefore the O 23 crew is not complete on this war patrol.
8 Sep 1940: During O 23's refit in the Camperdown Dock a spring of the conning tower hatch had been replaced. On O 23's first dive the hatch could not be closed. Therefore the submarine headed back to Dundee again, but before she arrived in Dundee the crew had repaired the hatch themselves. O 23 continued her original course again.
8 Sep 1940 at 16:00 hrs: O 23 sights a German plane. The submarine dives and is not spotted by the plane.
10 Sep 1940 at 10:00 hrs: O 23 is ordered to assist in the search for a British bomber crew. The bomber crashed into the sea only about 20 m away from O 23's current position. On 13:00 hrs the O 23 gets assistance from a Coastal Command airplane. Unfortunately no survivors (or any debris) is spotted. On 16:00 hrs the O 23 is ordered to return to her original patrol area.
20 Sep 1940: O 23 leaves her patrol area and heads for Dundee (Scotland).
21 Sep 1940 at 08:45 hrs: O 23 arrives in Dundee and moors at the King George V quay.
28 Sep - 20 Nov 1940: O 23 is under the command (temporarily) of Ltz. I A.M. Valkenburg
Somewhere between 22 Sep and 4 Oct: His Royal Highness Prince Bernhard visits the Dundee submarine base, he also inspects the O 23. Visit the G.B.M van Erkel page for a related image.
Period between the patrols: O 23 is docked for maintenance and the crew is on leave.
5 Oct - 20 Oct 1940: O 23 patrols off Norway. No attacks are made.
O 23 is the first Dutch and allied submarine during W.W.II that enters a Norwegian fjord while being submerged.
5 Oct 1940 at 14:00 hrs: O 23 departs from Dundee (Scotland).
8 Oct 1940: O 23 arrives in her patrol area, The patrol box is off Fejeosen Island, which is located on the Northern Route to Bergen (Norway). During the night they recharge the batteries.
9 Oct 1940 at 05:00 hrs: The boat submerges because of the dawn. At 05:45 the O 23 runs aground while being submerged at a depth of 70 feet. The submarine surfaces immediately. It turns out the boat is much closer to the coast than anticipated. During the remainder of the day the O 23 stays close to the coast. Only two airplanes and several trawlers (off Fejoesen) are spotted.
Night 9/10 Oct 1940: Because of a storm the O 23 sails to deeper waters, at a depth of 30 m they wait for the weather to improve.
11 Oct 1940: The storm settles and the O 23 returns to a position 1 or 2 nm off the coast.
13 Oct 1940: The O 23 enters the Hjelte Fjord. No ships are spotted. O 23 is the first Dutch and allied submarine during W.W.II that enters a Norwegian fjord while being submerged.
During the remainder of the patrol the weather is bad (rainy). O 23 only spots several Fishing boats, probably ASW trawlers, close to the coast.
18 Oct 1940: O 23 leaves the patrol area and heads for Dundee (Scotland)
20 Oct 1940 at 14:00 hrs: The O 23 arrives at the King George V quay in Dundee
After the usual docking period the boat is prepared for an other war patrol.
4 Nov - 19 Nov 1940: O 23 patrols off Norway. No attacks are made.
During this patrol the O 23 is equipped with a bridge windscreen. Because the screen was installed/designed quit hastily it did not meet the requirements.
4 Nov 1940 at 13:00 hrs: O 23 departs from Dundee (Scotland).
6 Oct 1940: O 23 arrives in her patrol area, The patrol box is off Fejeosen Island, which is located on the Northern Route to Bergen (Norway). At the entrance of Feje Fjord they spot two patrolling fishing boats.
Night of 6/7 Nov 1940: O 23 is ordered to a more southern patrol area, The new area is 60°00'N-03°20'E, off Kors Fjord (Norway).
Morning of 7 Nov 1940: Once again the O 23 is ordered to a more southern patrol area, The new area is 59°00'N-03°50'E, off Skudesnes Fjord (Norway). The frequent repositioning of O 23 is possibly because the Allies suspect that the German pocket battleship Admiral Scheer might return to a German port.
Night of 7/8 Nov 1940: O 23 arrives in her new patrol area.
Night of 9/10 Nov 1940: Due to a storm the O 23 can not maintain periscope depth. Therefore she dives to 25 m.
Evening of 10 Nov 1940: O 23 surfaces in order to recharge her batteries. At 20:00 hrs considerable amounts of water enter the control room via the conning tower hatch. The water causes a shortcut, which results in a fire. The fire is quickly extinguished but several electrical cables are destroyed. Therefore the port main motor is temporarily unavailable.
11 Nov between 12:00 and 16:00 hrs: The port main motor is up and running again.
13 Nov 1940: The storm settles, so the O 23 can return to periscope depth again.
13 Nov 1940 at 19:23 hrs: While being submerged the O 23 hears several heavy explosions.
13 Nov 1940 at 19:49 hrs: O 23 surfaces and spots a fire at bearing N130°E, and a vague silhouette which could be of a ship. In WWII the British Admiralty stated that: ". . . this might be connected with the so far unexplained loss of O 22 . . "
13 Nov 1940 at 20:00 hrs: O 23 is ordered to a more southern patrol area. The new area is 58°31'N-05°45'E off Obestad (Norway).
14 Nov 1940: O 23 arrives in her new patrol area. From her patrol position the O 23 can 'guard' the southern entrance to Stavanger (Norway).
15 Nov 1940: O 23 is patrolling 4 nm off the coast.
15 Nov 1940: The O 23 observes the shipping on the other side of the mine barrier. The O 23 tries to get into a good firing position by sailing into the dangerous area. This is quite a gamble because this area, area 'QZX 93', is designated by the British Admiralty as 'Possibly Mined'. But just after the O 23 got into position (5000 m) the target passed Jaederens Point.
After O 23's return to port the Senior Officer Dutch Submarines (SODS) concluded that the captain had taken too big a risk for such a 'small' target.
15 Nov 1940 at 21:00 hrs: O 23 spots a convoy of three ships at 5000 yards off the port bow. The captain decides for a surface attack. At a distance of 2500 yards ship #2 and #3 suddenly changes course, resulting in a starboard bow bearing. At a distance of 1000 yards the captain realizes that the ships are three Anti Submarine (AS) trawlers. Possibly the trawlers have already heard the O 23 and are moving in for the attack. The O 23 brakes off the attack and sails away from the coast at full speed. By observing the trawlers the captain concludes the enemy indeed heard the O 23 but did not yet spot his submarine. The rest of the night, and the following morning, the O 23 stays well away from the coast.
16 Nov 1940 in the morning: O 23 spots many airplanes, which are searching the coastal waters.
16 Nov 1940 late in the morning: The O 23 returns to a position 4 nm off the coast. The submarines spots some shipping inside the area that is possibly mined (area QZX 42). But no ships are attacked.
16/17 Nov 1940 at night: Because of the stormy weather the O 23 stays well away from the coast.
17 Nov 1940: The weather improves a bit and the O 23 returns to a position close to the coast. The submarine spots a small convoy, but the attack is broken off because the convoy is protected by several trawlers (equipped with ASDIC).
17/18 Nov 1940 at night: During a SE storm the O 23 leaves the patrol area and heads for Dundee (Scotland).
19 Nov 1940 probably in the evening: O 23 arrives in Dundee (Scotland).
20 Nov 1940 - 13 Nov 1941: O 23 is under the command of Ltz. I G.B.M. van Erkel.
During the last patrol the O 23 was equipped with a bridge windscreen. But because the screen was installed/designed quite hastily it did not meet the requirements. This problem is also solved during the following maintenance period in Rosyth and Grangemouth (both Scotland).
15 Dec 1940: O 23 is degaussed (de-magnetized) at Rosyth dockyard.
16 Dec 1940: While on its way back to Dundee the O 23 conducts some underwater radio-receiving trials.
18 Dec 1940 - 1 Jan 1941: O 23 patrols off Norway. No attacks are made.
20 Dec 1940 early in the morning: The O 23 arrives in her patrol area. The patrol area is Kors Fjord and Selbjorn Fjord, which are the Southern entrances to city of Bergen (Norway).
The first few days only one German airplane is spotted. Many screws and explosions are heard, probably from patrolling AS trawlers, but no ships are spotted.
23 Dec between 20:00 and 24:00 hrs: The O 23 spots a merchant (bearing West). But because of the dark night the contact is lost almost immediately. After an 30 min pursuit at full speed the O 23 returns to her patrol area.
27 Dec 1940: FOS orders the O 23 to the position 60°10'N-04°10'E in order to intercept enemy forces that are moving South along the Norwegian coast. O 23 arrives in the area on the same day.
28 Dec 1940 at 19:00 hrs: O 23 hears screw noises and surfaces immediately. Once on the surface they spot a passenger ship at a distance of 3 or 4 nm heading South. The ship is running at 17 kts and has all lights switched on ! The commander of the O 23 can not verify the nationality of the ship and, although he was ordered to attack he, only follows the ship. But because the submarine can only do 15 kts (due to the rough seas) the distance between the two ships increases rapidly.
Back in Dundee in turns out that the Swedish government had asked the British government permission for this ship to pass. The British Admiralty granted the request but did not inform FOS. Therefore the FOS could not inform the O 23 about this ship.
The comment of FOS (addressed to the Captain S. in Dundee) was:
" . . Although I think the Captain of O 23 should have carried out his orders, it was fortunate he decided not to do so . . ."
O 23 is ordered back to her original patrol area off Bergen.
30 Dec 1940: O 23 leaves the patrol area and heads for Dundee (Scotland).
31/1 Dec 1941 at night: The O 23 passes through the British mine barrier that is located along the coast. Because of the bad weather (heavy snow storms) the only means of navigation are depth sounding.
1 Jan 1941 at 08:00 hrs: O 23 passes Bell Rock (Scotland).
1 Jan 1941 at 11:00 hrs: O 23 moors at the King George V quay in Dundee (Scotland).
After this patrol it is conclude that the adjustments made on the wind screen were successful. So no further work on the wind screen is necessary.
19 Jan - 30 Jan 1941: O 23 patrols off Norway. No attacks are made.
19 Jan 1941 at 15:00 hrs: O 23 departs from Dundee and exercises (including dive plane operator exercises) off Bell Rock.
19 Jan 1941 at 17:00 hrs: The O 23 continues her transit to the patrol area, which is once again off Bergen (Norway). Due to the NE storm the O 23 is submerged for major part of this transit. Many explosions are heard, probably exploding drifting mines.
24 Jan 1941 between 12:00 and 16:00 hrs: O 23 arrives in her patrol area. The next morning the sight the Norwegian coast.
24 Jan 1941 at 15:10 hrs: There is an explosion close to the O 23. The submarine goes deep, changes course and increase speed. At 15:13 there is an other (smaller) explosion. At this moment the O 23 is 15 nm off the Norwegian coast and no ships were spotted or heard prior to the explosions. At 15:25 the sub returns to periscope depth, but there are no surface or air contacts.
A few weeks later in turned out that the Germans laid a large minefield off the coast. The minefield is located between Vikingbank and the North side of Cabbage Patch, it is 100 nm long and 20 nm wide. Because of this information the transit route to the area is changed. But the O 23 already crossed this mine field twice (transiting) during her Jan.1941 patrol.
During the remainder of the patrol the weather is good, but the O 23 only spots some fishing boats off Holmengraa (Norway).
30 Jan 1941: The O 23 is ordered to return to port. She leaves the patrol area at 18:00 hrs.
31 Jan 1940 in the morning: O 23 arrives in Dundee (Scotland).
During this period between patrols the commanders and officers train on the so called 'attack teacher'.
12 Feb - 17 Feb 1941: O 23 patrols off Norway. No attacks are made.
12 Feb 1941 at 15:30 hrs: O 23 departs from Dundee and sails to her patrol area off Bergen (Norway).
14 Feb: O 23 arrives in her patrol area. The same day the O 23 ordered back to port. On the way back an large explosion (probably a drifting mine) is heard, or noticed.
16 Feb 1941 at 04:25 hrs: Suddenly a bright light is spotted right above the sub. The light is probably a signal star, luckily the chute of the star did not open, The O 23 immediately dives to 30 m, but no surface activity is spotted, and the O 23 continues her journey.
17 Feb 1941: O 23 arrives in Dundee (Scotland). The reason that O 23 was called back was the fact that the O 23, and the O 21, had to go to the Mediterranean Sea.
20 or 21 Feb 1941: Until now only the commander of the O 23 new about the transit to the Mediterranean Sea. But on the 20th or 21st the officers and the crew are also informed.
The following days are used for loading supplies, spare parts, torpedoes (mixed load of 10x45 and ?x53 cm torpedoes), fuel, degaussing, adjusting the compasses etc.
23 Feb - 10 Mar 1941: O 23 is on convoy duty on the route Dundee-Gibraltar. No attacks are made.
24 Feb 1941 at 14:00 hrs: Under the escort of HMS White Bear the O 23 and O 21 depart from Dundee and sail via Pentland Firth to the Irish Sea. In the Irish Sea HMS White Bear is relieved by the Mine Sweeper FFS La Moqueuse.
26 Feb 1941: O 23, O 21 and FFS La Moqueuse pick-up an electric generator at Holyhead harbour (Wales). They only visit the port for a few hours.
27 Feb 1941: Off the Welsh coast the submarines are shelled by the English merchant Losada.
Because the escort vessel is sailing behind the submarines the captain of the Losada spots the submarines before he spots FFS La Moqueuse, and therefore thinks he encountered some German U-boats and starts shelling the subs. To prevent any direct hits the subs have to dive.
FFS La Moqueuse is unaware of the fact that both submarines are submerged, but she does spot the periscope of O 21. Unfortunately the captain of La Moqueuse also thinks he spotted a U-boat and therefore starts launching depth-charges. The O 21, which sustains some light damage, surfaces immediately and the captain of La Moqueuse realizes his mistake.
28 Feb 1941 at 06:00 hrs: Due to the bad weather off Trevose Head (England) the FFS La Moqueuse breaks off her escort duties and heads for a safe harbour. From know on both subs are on their own.
O 23 and O 21 sail via Lands End to the Scilly islands. After the Scilly islands the boats submerge during the day and therefore O 21 and O 23 soon lose contact. Since both boats have different orders they take different routes to Gibraltar. O 23 has no special orders and therefore she sails "straight" to Gibraltar.
10 Mar 1941: O 23 arrives in Gibraltar.
Inspection of the torpedoes shows that 7 (out of the 10) 45 cm MK IV British torpedoes have serious malfunctions. A board of Inquiry was formed and the board concludes that the contact pistols have to be altered.
Mar - Sep 1941: O 23 is attached to the 8th Flotilla in Gibraltar and is under British operational control.
24 Mar - 3 Apr 1941: O 23 escorts convoy HG 57 (Gibraltar - U.K.) until 45°N.
24 Mar - 11 Apr 1941: O 23 patrols the Bay of Biscay and the Atlantic Ocean. No attacks are made.
3 Apr - 11 Apr 1941: O 23 escorts convoy OG 57 (U.K. - Gibraltar), she engages the convoy at 45°N.
23 Apr - 2 May 1941: O 23 escorts convoy HG 60 (Gibraltar - U.K.) until 45°N.
3 May - 10 May 1941: O 23 escorts convoy OG 60 (U.K. - Gibraltar), she engages the convoy at 45°N.
25 May - 1 June 1941: O 23 escorts convoy HG 63 (Gibraltar - U.K.) until 45°N.
1 June - 7 June 1941: O 23 escorts convoy OG 63 (U.K. - Gibraltar), she engages the convoy at 45°N.
24 June 1941: The O 23 is prepared for her next patrol.
25 June - 10 July 1941: O 23 patrols the Ligurian Sea.
25 June at 21:30 hrs: O 23 departs from Gibraltar and sails to her patrol area, between Livorno and Elba, in the Ligurian Sea. She takes a route along the Spanish East coast and North of the Balearic Islands.
29 June 1941: O 23 arrives at the Northern tip of Corsica (France).
29 June 1941 at 21:30 hrs: O 23 sails between the islands Gorgona and Capraia is the direction of the Italian coast toward a point South of Vada Rock.
30 June 1941 at 3:00 hrs: O 23 submerges and an hour later she spots a grey hull. The commander launched two Mark Xxx torpedoes with a 10 second interval. Both torpedoes miss the +/- 2000 t freighter. Because the target is not real impressive (besides ballast it has no cargo) the commander decides not to launch any other torpedoes. He wants to keep his presence a secret and wants to wait fort a better target. After about 20 minutes there is an explosion, this is probably from one of the torpedoes
30 June at 05:00 hrs: O 23 spots a patrol vessel South of Vada Rock. The vessel sailed out of sight on the Southern course.
Next the O 23 spots a small freighter, which is regarded as a good target. Unfortunately the freighter takes she route between Vada Rock and the Italian coast. The following two Merchants take exactly the same route. Because of the shallow waters off Vada Rock the O 23 can not attack and therefore the O 23 heads for the Southern entrance of the channel between the shallow waters and the Italian coast. But by now the three spotted vessels are out of sight.
30 June at 11:00 hrs: O 23 spots a large vessel that is sailing a Northern course. The target turns out to be a fully loaded tanker. At 12:00 or 13:00 hrs the O 23, at that time only half a mile off the coast, is in a good attack position. The tanker is approximately 1 mile off the coast and has a speed of +/- 9 kts. The O 23 launches 4 torpedoes with a 15 seconds interval. Three torpedoes hit the tanker, one forward, one below the bridge and one aft below the funnel. Shortly after the hits the tanker capsizes and sinks in waters of about 80 meters. Position: 43°06'N-10°26'E, 7nm north west of San Vincenzo (Livorno), Ligurian Sea. The Dutch commander reports the target being 8000t. But the target, the Italian tanker SS Capacitas, is only 5371t.
Because reliability of the Dutch V53 torpedoes as well as the English Mark IV** torpedoes was still under discussion at that time the commander decided to use 2 of both.
Pre war photo of Ansaldo IV. Genova harbour. (Photo: © 'Archivio Ansaldo' n°22980)
The original name of the 5371 ton Capacitas is Ansaldo IV. She is owned by Soc. An. Mare Nostrum from Genova (Italy) and build by Cantieri Navali Ansaldo-San Giorgio Muggiano (La Spezia). For her last voyage she loaded at Napoli and planned to unload at Genova. Dimensions 118,5 x 15,75 x 8,57 meters. Armament with Ansaldo 75mm A.A. gun .
Drawing of the Capacitas wreck, Aug 2000. (Drawing: Silvia Innocenti).
In 1996 an Italian diving team named "Wreck Project Research", located the wreck of the Capacitas. It lies at a maximum depth of 80 meters, between Marina di Cecina (Livorno, Italy) and San Vincenzo (Livorno, Italy). The location is 43°06'N-10°26'E.
O 23 spots that a patrol vessel and en several fishing boats are heading towards the tanker's last position. The commander decides to dive deep and head for the opening between the Corgona and Capraia Islands.
30 June 1941 at 15:00 hrs: The O 23 returns to periscope depth and becomes aware that one of her fuel tanks must be leaking. The result is an oil trail that can be spotted quit easily by the enemy. Further investigation shows that main tank five is leaking heavily. The only solution is to drain the tank inboard. Fortunately the draining is successful and soon the oil slick disappears, but it already has been spotted by an Italian flying boat and a little later the screws of two destroyers are heard. One of these boats sails exactly over the submarine, but fortunately they head towards the end of the oil slick. Since their search and the end of the slick is unsuccessful the enemy vessels start searching on the main ax of the slick. But after several hours the distance between the O 23 and the enemy vessels has increased to such an extent that the submarine can not hear the destroyers anymore.
Vice Admiral G.T.B. Edward-Collins comments on O 23's patrol report where: " . . .Great credit is due to the commanding officer of H.N.M.S. O 23, Lieutenant Commander G.B.M. van Erkel for this successful attack which resulted in the destruction of a valuable enemy tanker, and for the skilful manner in which he evaded the two Italian destroyers in spite of the oil-fuel leak which disclosed his presence . . ."
30 June 1941 at 21:30 hrs: The O 23 surfaces and sails with a speed of 16 1/2 kts between Corgona and Capraia Island to open waters.
The commander decides to sail to a point far West of Corsica in order to find out what is wrong with the tank.
2 July 1941 in the late afternoon: The O 23 stops at a position off the Spanish East coast, approximately 20 mile off Cape Creus in order to inspect the superstructure. It turns out that the manhole cover of main tank five had sprung leak over a length of 15 centimetres. After transferring the fuel to other tanks it showed that the submarine had lost +/- 16 tons of fuel.
?17 July 1941 at 21:00 hrs: O 23 damages (torpedo attack) the Italian tanker Maddalena Odero (built 1921, 5479t). Dutch sources show no attack at the 17th of July. They report an attack on the Maddalena Odero (possibly) on the 16th of August. According to Dutch sources the O 23 was not on patrol on the 17th of July 1941.
The book "Navi mercantili perdute" (Lost merchant ships), Rome 1997, from the Italian Navy Historical Branch reports that the Maddalena Odero (a 1921 built 5479 ton freighter) was attacked on 17 Aug 1941 at 21:00 hrs by an enemy submarine near Lampedusa island and ran herself ashore at Cala Croce (Lampedusa) at 07:00 hrs on 18 Aug. That same day at 13:30 hrs the damaged ship was set ablaze by 5 Blenheim bombers from Malta No.105 Squadron.
We are still looking for a photo of Maddalena Odero. Do you have one ? Then please contact us at firstname.lastname@example.org.
2 Aug - 20 Aug 1941: O 23 patrols the southern part of the Tyrrhenian Sea.
?16 Aug 1941: O 23 damages an Italian freighter (possibly the 5479 t ss Madalena Odero). Other sources report O 23 fired four 15000yd long-range torpedoes at an unknown steamer at 39°35'N-13°18'E. The torpedoes missed the target (although the Dutch commander thought he scored two hits). These sources report the attack on the Madalena Odero on the 17th of July.
The book "Navi mercantili perdute" (Lost merchant ships), Rome 1997, from the Italian Navy Historical Branch reports that the Maddalena Odero was attacked on 17 Aug 1941 at 21:00 hrs by an enemy submarine near Lampedusa island and ran herself ashore at Cala Croce (Lampedusa) at 07:00 hrs on 18 Aug. That same day at 13:30 hrs the damaged ship was set ablaze by 5 Blenheim bombers from Malta No.105 Squadron.
We are still looking for a photo of Maddalena Odero. Do you have one ? Then please contact us at email@example.com.
20 Sep 1941: O 23 returns to Dundee (Scotland) for repairs.
Sep 1941 - Mar 1942: O 23 is refitted in the U.K.
13 Nov - 30 Dec 1941: O 23 is under the command of Ltz. I K. van Dongen.
7 Dec 1941: The USA declares war on Japan after Japanese forces attack Pearl Harbour. Approximately 7 hours after the attack the Netherlands also declares war on Japan.
14 Dec 1941: Japanese planes bomb Tarempah (Anambas Islands) which is Netherlands East Indies territory.
27 Dec 1941: Japanese invaders occupy Tambelan Islands, Dutch territory, between Borneo and Singapore.
30 Dec 1941 - 23 Feb 1944: O 23 is under the command of Ltz. I A.M. Valkenburg.
16 Mar 1942 - 13 May 1942: O 23 departs the U.K. and sails to the Dutch East Indies, she takes the route via the Mediterranean.
May 1942 - ?: O 23 is based in Colombo and attached to the 4th Flotilla. She is under British Eastern Fleet operational control.
During the transit from the U.K. several technical problems are located. Therefore the O 23 first has to be repaired in Bombay before going on war patrol.
16 May 1942: Submarines O 23, O 19, HMS Scout and tender Colombia depart Colombo and head for Bombay. The ships arrive the same day.
At the Naval Dock yard in Bombay O 23's anchor is replaced by a spare one and the cooling machine receives a check up.
23 and 24 May 1942: 12 Crew members of the O 23 are awarded the 'Bronzen Kruis'
29 May 1942: Head Engineer Off. MSD 1kl F.J. de Hoop passes away at the St. George Hospital, Bombay. He is buried at the Sewry / Sewri Cemetery that same day. Please email us if you have more information on F.J. de Hoop his death.
3 Jul 1942: After a sea trial off Bombay the O 23 is ready for active duty again.
Jul 5 1942: O 23 departs Bombay and heads for Colombo.
Jul 9 - Jul 18 1942: O 23 conducts standard and ASDIC exercises.
18 Jul 1942: The commander of O 23 receives Patrol Order #9 from Senior Officer Submarines Colombo.
19 July - 10 Aug 1942: O 23 patrols the Northern part of the Malacca Strait.
19 Jul 1942 at 17:30 hrs: O 23 departs Colombo for her first war patrol in Indonesian waters.
25 Jul 1942 between 00:00 and 04:00 hrs: The O 19 arrives in her patrol area.
26 Jul 1942: While patrolling North of Penang several fishing boats are spotted.
27 July 1942: O 23 attacks the Japanese coastal vessel ms Shofuku Maru 2 (730t, but 800-100t reported). The enemy vessel is doing 8kts on a Northern course and her position is 05°07'N-98°50'E, south-west of Penang.
At 07:25 hrs: Two German torpedo's type G7AD are fired from the bow tubes from a distance of 700yds. The running depth's are set to 2m and 3m. The standard depth setting of these torpedoes is 3m, but the commander had heard that in good weather 2m is also possible. The torpedo that was set to 2m jumps out of the water several times and her course was off to starboard. No explosions were heard, therefore the submarine surfaces and attacked the vessel with gunfire.
At 07:32 hrs: The first deck gun round is fired from a distance of 800yds. It turns out that the enemy vessel is unarmed and the O 23 starts closing in on the Japanese vessel. Unfortunately the 10th round gets jammed in the deck gun's barrel. Of these 9 rounds only one was a hit. The Oerlikon machinegun takes over from the deck gun. Unfortunately the 80th round gets jammed in the machine gun's barrel Although several hits are reported the vessel still floats. The vessel is running very shallow so a torpedo can not be used to sinks here.
At 07:45 hrs: O 23 retreats on a S-W course.
We are still looking for a photo of ms Shofuku Maru. Do you have one ? Then please contact us at firstname.lastname@example.org.
29 July 1942: West of Poeloe Perak, in the middle of Malacca Strait, the O 23 attacks a Japanese Cruiser.
The Japanese group consists of two cruisers of the Takao or Mogami class protected by four destroyers of the Hubuki class. The zig-zagging group is spotted at a distance of approx. 7nm.
29 July 1942 at 06:00 hrs: The commander knows it will be a gamble for the German G7 AD type torpedoes but at a distance of about 5500m he fires all 4 bow torpedoes. Unfortunately the torpedoes miss their target. A long depth-charge counter attack is the only result. After firing the torpedoes the additional water in the tubes makes it is quite difficult to maintain a good trim
29 July 1942 at 06:12: Two explosions are heard, but since the running time of the torpedoes is 7min these explosions are probably depth-charges. A quick look through the periscope learns that a cruiser and a destroyer are heading towards the O 23. It looks like the commander can get the O 23 in a good position to use the deck tubes, but since the trim is still no good it is impossible to keep the sub at periscope depth. The crew does try to launch by using the listening device, but unfortunately it is impossible to distinguish between the cruiser's and the destroyer's screw noises. Meanwhile more depth charges explode. At a depth of 80 feet a thermal layer is located and with the 'help' of this layer and by running in silent mode the O 23 can sneak away.
29 July 1942 at 08:48 hrs: There have been no nearby screw noises for over half an hour, so the O 23 comes to periscope depth. At a distance of 4 miles a searching destroyer is spotted. Since the destroyer is searching in the wrong direction the O 23 dives to 80 feet again in order to prevent being spotted by enemy planes. The sub comes to periscope depth every half hour.
29 July 1942 at 10:11 hrs: Five faint explosions are heard and at10:21 four faint explosions are heard.
29 July 1942 at 10:43 hrs: Just after coming to periscope depth the O 23 spots two Wakataka class destroyer and two other ships (looking like sub hunters) at only half a mile distance dead ahead. O 23 immediately changes course to starboard. After two min the commander takes another peak and the ships are now on only 300 yds off the starboard bow, so the O 23 changes course to port.
29 July 1942 at 10:50 hrs: Three faint explosions are heard.
29 July 1942 at 12:00 hrs: O 23 returns to periscope depth. No ships are spotted. Since the enemy will be looking for O 23 west of Poeloe Perak the O 23 set course to the area East off Poeloe Perak.
29 July 1942 at 18:30 hrs: O 23 surfaces and with a speed of 13 kts. she heads for the N-W part of her patrol area. Attempts to report (by radio) the location of the enemy are unsuccessful.
29 Jul 1942 at 21:45 and 23:15 hrs: O 23 spots several ships that look like destroyers. At midnight O 23's position is 40 miles N-W off Perak.
The following days the O 23 patrols N-W and N off Perak and between Perak and the Bunting islands. She only spots some fishing boats.
2 Aug 1942: O 23 starts patrolling in the waters North of Penang once again.
2 Aug 1942 at 08:42 hrs: O 23 spots a enemy convoy. The convoy consists of 4 merchant ships of 3000-5000 tons that are preceded (5 miles) by an armed merchant of about 4000 tons.
2 Aug 1942: O 23 sinks the Japanese freighter ms Zenyo Maru (6441t). Position: 05°36'N-99°53'E, off Penang. The freighter is hit port side in engine room. 27 men are killed and the vessel is burned out and abandoned. At a later unknown date the wreck is towed to Singapore and scrapped.
We are still looking for a photo of ms Zenyo Maru. Do you have one ? Then please contact us at email@example.com.
2 Aug 1942: O 23 sinks the Japanese transport ss Ohio Maru (5872t). O 23 fires two torpedoes of which one hits the target. Position: Malacca Strait, off Penang.
We are still looking for a photo of ss Ohio Maru. Do you have one ? Then please contact us at firstname.lastname@example.org.
Both ships, sunk on the 2nd of August, were are of a group of five Japanese ships. The O 23 first fires her last bow-torpedo. After making a 90' turn she fires two torpedoes from the external-traversing-tubes, which are turned 90'. The last two torpedoes are, after an other 90' turn, from the aft-tubes.
On the way back home the O 19 transits via Poeloe Weh in order to recon the area off Sabang, but this can not be confirmed by Patrol Order #9
1 Sep - 19 Sep 1942: O 23 patrols the Strait of Malacca (Patrol Order #11). No attacks are made.
17 Oct - 7 Nov 1942: O 23 patrols the Strait of Malacca.
25 Oct 1942: O 23 attacks a Japanese convoy and damages the freighter ms Shinyu Maru (4621t), one torpedo hits the freighter.
The torpedoes fired at a second vessel miss because the ship, warned by the hit on the Shinyu Maru, changes her course. Position: 05°28'N-99°56'E, off Penang.
After the war it came out that it was a very 'fortunate miss', because at that time there were 1700 Dutch POWs, transported from Java to Rangoon, on board the second ship.
We are still looking for a photo of ms Shinyu Maru. Do you have one ? Then please contact us at email@example.com.
28 Nov - 20 Dec 1942: O 23 patrols the Strait of Malacca. No attacks are made.
22 May - 6 June 1943: O 23 patrols the Strait of Malacca. No attacks are made.
15 June - 6 July 1943: O 23 patrols the Strait of Malacca. No attacks are made.
24 June - 16 July 1943: O 23 patrols the Strait of Malacca. No attacks are made.
25 June 1943: Near the Sembilan Islands a SOE group, Captain J.C.H. Davis and a Chinese man, is transferred from a Junk to the O 23, code name 'Gustavus II'.
Read the book Operations Most Secret for a detailed description of this (and many other) secret SOE operation.
4 Aug 1943: Near the Sembilan Islands a SOE group, consisting of Captain J.C.H. Davis, 3 Chinese men and supplies, are transferred to a Junk. Code name of this operation is 'Gustavus II'.
Sep - ? 1943: O 23 sails to the U.K. for refitting. She takes the route via the Mediterranean. In the western part of the Indian Ocean O 23 unsuccessfully tries to overtake/attack a Japanese submarine.
5 Nov 1943 - Feb 1945: O 23 arrives in Dundee (Scotland) and is refitted. During her stay in Dundee she is attached (not 100% certain) to the 9th Flotilla.
23 Feb 1944 - 16 Mar or 17 Apr 1946: O 23 is under the command of Ltz. I A.J. Schouwenaar.
Feb 1945 - ?: O 23 is attached to the 3rd Flotilla.
26 Mar - 28 June 1945: O 23 is moored at the Rotterdam submarine base in the Netherlands.
8 May 1945: Germany surrenders.
17 July 1945: O 23 departs from Holy Loch (Scotland) and sails to the Dutch East Indies.
Aug 1945: O 23 arrives in Australia, but the war with Japan is already over. She is based at Fremantle.
5 Aug 1945: ?Under the command of Ltz. I A.M. Valkenburg? O 23 conducts a reconnaissance mission to the south coast of Java.
15 Aug 1945: Japan surrenders.
Oct - Nov 1945: O 23 evacuates a NEFIS party from the Paternoster islands (north of Sumbawa island) to Makassar.
Late Oct: From late Oct she probably (not confirmed) also patrols the Sunda Strait. A typical patrol would take 7-10 days and numerous vessels would be stopped and searched.
21 Jan - 13 Mar 1946: O 23 departs from the Dutch East Indies and sails to Rotterdam (the Netherlands).
Feb 1946: O 23 evacuates naval personnel from Bangkok to Colombo.
13 Mar 1946: O 23 arrives in Rotterdam (the Netherlands).
1 May 1947 - 1 Jan 1948: O 23 is under the command of Ltz. II R. van Wely.
22 Jul - 11 Aug 1947: O 23 and Zwaardvisch (1) sail to the Dutch West Indies. The submarines are part of a temporary division that is under the command Capt. W.F. van Vreeswijk (flagship Van Kinsbergen).
11 Aug 1947: The ships arrive in Curaçao.
13 Oct - 31 Oct 1947: O 23 and Zwaardvisch (1) return to the Netherlands. The submarines are part of a temporary division that is under the command Capt. W.F. van Vreeswijk (flagship Van Kinsbergen).
31 Oct 1947: The ships arrive in Rotterdam (the Netherlands).
1 Jan - 1 Dec 1948: O 23 is under the command of Ltz. II H.M. van der Veen.
The submarine is mainly used for 'inschieten' (exercise lauches and runs) of torpedos off Den Helder.
1 Dec 1948: O 23 is decommissioned.
Apr 1949: O 23 is stricken and sold for scrap.
The Dutch surface ship van Speyk is refitted with the two former Sulzer diesel engines of the O 23.
|O 23 related pages|
|O 21 class specifications|
|O 21 class photos|
|O 23 boat history|
|O 23 related books|
|Operations Most Secret|
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